PIREX II — A new irradiation facility for testing fusion first wall materials

Abstract

A new irradiation facility, PIREX II (Proton Irradiation Experiment), became operational in March 1987. It is located on a dedicated beam line split from the main beam of the 590 MeV proton accelerator at the Paul Scherrer Institute (PSI). Irradiation with protons of this energy introduces simultaneously displacement damage, helium and other impurities. Because of the penetration range of 590 MeV protons, both damage and impurities are homogeneously distributed in the target material. The installation has its own beam line optics that can support a proton current of up to 50 μA. At a typical beam density of 4 μA mm 2 , the damage rate in steel is 0.7 × 10 −5 dpa s (dpa: displacements per atom), and the helium production rat He/dpa. Both flat tensile specimens of up to 0.4 mm thickness and tubular fatigue samples of 3 mm diameter can be irradiated. Cooling of the sample is performed by flowing pressurized helium gas over the sample. Irradiation temperatures can be controlled between 100 ° C and 800 ° C. Installation of an in situ low cycle fatigue device is foreseen. Beams of up to 20 μA have been obtained, the beam having an approximately Gaussian distribution of elliptical cross section with 4σ x between 0.8 and 8 nun by 4σ y of up to 10 mm. Irradiations for a dosimetry program have been completed on samples of Al, Cu, Fe, Ni, Au, W, and 1.4914 ferritic steel. The evaluation of results allows the correct choice of reactions to be used for determining total dose, from the standpoint of half life and gamma energy. A program of irradiations on candidate materials for the Next European Torus (NET) design (Cu and Cu alloys, 1.4914 ferritic martensitic steel, W and W-Re alloys and Mo and Mo alloys), where the above mentioned characteristics of this type of irradiation can be used advantageously, is now under way.